1. Technical Field
The invention relates to the handling of container bodies and in particular to a method and an apparatus for separating a series of container bodies, and methods and apparatus for bringing container bodies together.
2. State of the Art
As is known, container bodies, and in particular can bodies, are transported on conveyor belts with the body lying or suspended in the prone position, and subsequently have to be turned through 90.degree. for further processing, so that the can body is carried onwards in the upright position. FIG. 1 shows, highly schematically, an apparatus for carrying out this manoeuvre. A series of can bodies 2, of which only four are shown, are transported on a first conveyor belt 1, at a speed V1, and with a gap of approximately 3 to 4 mm between the can bodies. At this stage the can bodies are held on the conveyor belt e.g. by permanent magnets. The can bodies are to pass on to a further conveyor belt 4 on which they are stood upright in order to undergo further processing in a known manner. The can bodies cannot be transferred directly from the conveyor belt 1 to the conveyor belt 4, as the gap between the can bodies is so small that this would result in collision between successive can bodies. Another conveyor belt 3 is therefore interposed between the conveyor belt 1 and the belt 4, and is run at a speed V2 which is higher than the speed V1. This results in an increased gap between the can bodies on the belt 3, as the figure shows. Each can body 2 arriving at the conveyor belt 4 is then at a sufficient distance from the next can body to allow it to be picked up and conveyed away by the conveyor belt 4 before the next body lands the belt 4. The arrangement in FIG. 1 is highly schematic, and is shown without the known means for fixing the can bodies e.g. to the belt 4. The can bodies are held on the conveyor belts 1 and 3 preferably by magnetic force, as has already been mentioned, and as is also known.
Because machines used for the fabrication of can bodies, especially roller seam welding machines, are capable of operating at ever-increasing speeds, the problem arises that the speed V1 is already very high. For example it may be that 1000 bodies per minute are being transported on the conveyor belt 1, which means that the conveyor belt has to be travelling at high speed. Because the speed V2 of the belt 3 must be higher than the speed V1 in order to increase the gap between the can bodies, the resulting speed V2 is so high that transfer to the conveyor belt 4 becomes problematic, as the can bodies impinge on the conveyor belt 4 at high speed. U.S. Pat. No. 5,423,410 proposes, as a way of solving the problem, that the stream of cans be separated into two streams, using two parallel conveyor belts lying in the same plane. A transfer device pushes individual can bodies from one belt on to the other parallel belt. The can body has to traverse a relatively large distance in making this transfer, and the transfer from one belt to the other is made abruptly, which may cause damage to the body. On the one hand there is therefore the aim of providing a method and/or an apparatus whereby can bodies, even if conveyed at a rapid rate, can be divided between two or more belts, without any problem, and in the gentlest possible manner, for further processing.
Furthermore, some of the can bodies transported at a rapid rate on the conveyor belt 1 may need to be removed from the conveyor belt because they have been identified as defective by a quality control system. These bodies must be sent on for further processing. A known solution is to eject such bodies from the conveyor belt 1 e.g. by a jet of air. The result is that the ejected body leaves the belt at high speed, in an uncontrolled manner. If for example ejection takes place before the inner coating of the can body has dried, this ejection from the conveyor line causes coating powder or coating lacquer to be dispersed over the surrounding area, which is undesirable. Therefore, there is the further problem of providing a method and an apparatus by means of which individual can bodies may be removed, in a controlled manner, and in the gentlest possible way, from the series of can bodies being transported on a conveyor belt 1. GB-A 2114083 discloses a can body switch in which the stream of bodies is divided at a break-point of the conveyor belt by means of electromagnets arranged on either side. This arrangement is expensive, and at high rates of transfer may lead to malfunctions due to the absence of a positive grip and to high centrifugal forces.